I just got an email from Caligari the other day, offering me to upgrade to trueSpace 7.0 for $299. One of the new features is (claimed) virtually final render quality in real-time display.

DX9-based real-time photorealistic engine with silky smooth interaction during modeling, surfacing, lighting or animation of 1M+ polygon models. With soft shadows, anti-aliasing, projector lights and glows, it is good enough for photorealistic pre-visualisation of your animations, and in some cases for final rendering to video.

I don't think I'm going for the upgrade though. I'm too busy with C5Pro, and so far it's doing a great job for me.

Only so much $$, and time!